LONG TERM OBJECTIVES: This Project seeks to define normative aging of the cardiovascular system by means of dynamic analysis of blood pressure and core temperature variations observed by 24 h ambulatory monitoring. Ultradian rhythms of systolic blood pressure (SBP) will be tested as markers of normative aging in well old subjects aged 60 years or older who are leading active lives in the community. Methods of linear and nonlinear spectroscopy will be used to extract circadian and ultradian rhythms. Our SPECIFIC AIM is to test the hypothesis that intrinsic aging leads to a shift in temporal organization away from circadian and toward ultradian periods. We conjecture that the fundamental ultradian period exposed by aging is the thermal equilibrium time of 3 h. We further hypothesize that progressive dynamic instability in aging leads to a tightening of the coupling between cardiovascular pressure potential variations and metabolic-thermal processes in the ultradian domain. Isolated systolic hypertension emerges as a dynamic disease based in part on that tightening or increasing "dynamic rigidity". CLINICAL IMPLICATIONS: This study will provide needed norms for systolic pressure over the course of aging in well cohorts. Furthermore, the postulated (and already observed) ultradian rhythms of SBP can serve as a new marker of cardiovascular age in normotensive subjects.